U.S. patent application number 15/771516 was filed with the patent office on 2019-02-21 for image sensing device.
This patent application is currently assigned to SONY SEMICONDUCTOR SOLUTIONS CORPORATION. The applicant listed for this patent is SONY SEMICONDUCTOR SOLUTIONS CORPORATION. Invention is credited to Kazuaki HATABU, Yukihide KEIGO.
Application Number | 20190057999 15/771516 |
Document ID | / |
Family ID | 57227036 |
Filed Date | 2019-02-21 |
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United States Patent
Application |
20190057999 |
Kind Code |
A1 |
HATABU; Kazuaki ; et
al. |
February 21, 2019 |
IMAGE SENSING DEVICE
Abstract
An imaging device comprises a first pixel disposed in a
substrate. The first pixel may include a first material disposed in
the substrate, and a second material disposed in the substrate. A
first region of the first material, a second region of the first
material, and a third region of the second material form at least
one junction. A first lateral cross section of the substrate
intersects the at least one junction, and a second lateral cross
section of the substrate intersects at least one fourth region of
the first material.
Inventors: |
HATABU; Kazuaki; (Kumamoto,
JP) ; KEIGO; Yukihide; (Kumamoto, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SONY SEMICONDUCTOR SOLUTIONS CORPORATION |
Kanagawa |
|
JP |
|
|
Assignee: |
SONY SEMICONDUCTOR SOLUTIONS
CORPORATION
Kanagawa
JP
|
Family ID: |
57227036 |
Appl. No.: |
15/771516 |
Filed: |
October 21, 2016 |
PCT Filed: |
October 21, 2016 |
PCT NO: |
PCT/JP2016/081239 |
371 Date: |
April 27, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/14643 20130101;
H01L 27/14641 20130101; H01L 27/1461 20130101; H01L 27/14607
20130101; H01L 27/14812 20130101 |
International
Class: |
H01L 27/146 20060101
H01L027/146; H01L 27/148 20060101 H01L027/148 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2015 |
JP |
2015-217858 |
Claims
1. An imaging device, comprising: a first pixel disposed in a
substrate, the first pixel including, a first material disposed in
the substrate, and a second material disposed in the substrate,
wherein a first region of the first material, a second region of
the first material, and a third region of the second material form
at least one junction, wherein a first lateral cross section of the
substrate intersects the at least one junction, and wherein a
second lateral cross section of the substrate intersects at least
one fourth region of the first material.
2. The imaging device of claim 1, wherein the at least one fourth
region of the first material occupies a greater amount of surface
area in the second lateral cross section than the first region of
the first material and the second region of the first material
occupy in the first lateral cross section.
3. The imaging device of claim 1, further comprising: an electrode
on the substrate to read out electric charge.
4. The imaging device of claim 1, wherein the first material is an
n-type material, and the second material is a p-type material.
5. The imaging device of claim 1, wherein the first material is an
n-type material and the second material is an insulating
material.
6. The imaging device of claim 1, wherein the first lateral cross
section is taken closer to a light incident side of the first pixel
than the second lateral cross section.
7. The imaging device of claim 1, wherein the first material and
the second material form a lattice structure in the first lateral
cross section.
8. The imaging device of claim 7, wherein the first material and
the second material are in a checkered pattern.
9. The imaging device of claim 7, wherein the first material forms
a grid of n columns and m rows in the second material.
10. The imaging device of claim 7, wherein the second material
forms a grid of n columns and m rows in the first material.
11. The imaging device of claim 1, wherein the first material and
the second material have linear shapes in the first lateral cross
section.
12. The imaging device of claim 1, further comprising: a charge
accumulation region disposed in the substrate.
13. The imaging device of claim 12, wherein the at least one fourth
region of the first material occupies a greater amount of surface
area in the second lateral cross section than the first region of
the first material and the second region of the first material
occupy in the first lateral cross section.
14. The imaging device of claim 12, further comprising: a second
pixel, wherein the first pixel and the second pixel share the
charge accumulation region.
15. The imaging device of claim 14, further comprising: a first
electrode on the substrate of the first pixel; and a second
electrode on the substrate of the second pixel, wherein the first
electrode and the second electrode readout electric charge from the
charge accumulation region.
16. The imaging device of claim 15, wherein the first pixel and the
second pixel are adjacent to one another and the charge
accumulation region is between the first electrode and the second
electrode.
17. The imaging device of claim 12, further comprising: a second
pixel, a third pixel, and a fourth pixel, wherein the first pixel,
the second pixel, the third pixel, and the fourth pixel share the
charge accumulation region.
18. The imaging device of claim 17, further comprising: a first
electrode on the substrate of the first pixel; a second electrode
on a substrate of the second pixel; a third electrode on a
substrate of the third pixel; and a fourth electrode on a substrate
of the fourth pixel, wherein the first electrode, the second
electrode, the third electrode, and the fourth electrode readout
electric charge from the charge accumulation region.
19. The imaging device of claim 18, wherein the first pixel, the
second pixel, the third pixel and the fourth pixel are in a
2.times.2 matrix, and the charge accumulation region is at a center
portion of the 2.times.2 matrix.
20. The imaging device of claim 19, wherein the charge accumulation
region is surrounded by the first electrode, the second electrode,
the third electrode and the fourth electrode.
Description
TECHNICAL FIELD
[0001] The present technology relates to an image sensing device
and/or pixel in an imaging device. More particularly, the present
technology relates to an image sensing device and/or pixel in an
imaging device that improves a saturated signal electric charge
quantity.
CROSS REFERENCE TO RELATED APPLICATIONS
[0002] This application claims the benefit of Japanese Priority
Patent Application JP 2015-217858 filed Nov. 5, 2015, the entire
contents of which are incorporated herein by reference.
BACKGROUND ART
[0003] A CCD (Charge-Coupled Device) image sensor is an image
sensor that arranges two-dimensionally photoelectric conversion
devices (e.g., photodiodes) corresponding to pixels, and reads out
signals of respective pixels that are electric charges provided by
the photoelectric conversion devices using a vertical transfer CCD
and/or a horizontal transfer CCD.
[0004] On the other hand, a CMOS (complementary
metal-oxide-semiconductor) image sensor is similar to the CCD image
sensor in that the photoelectric conversion devices corresponding
to pixels are two-dimensionally arranged, but does not readout
signals using the vertical and horizontal transfer CCDs, and
instead reads out the signals stored per pixel from the pixels
selected using selection lines configured of aluminum, copper wire,
etc. like a memory device.
[0005] As described above, the CCD image sensor and the CMOS image
sensor are different in many points such as a readout method, but
are common to have photodiodes.
[0006] A maximum value of a signal electric charge quantity
accumulated on the photoelectric conversion devices is referred to
as a saturated signal electric charge quantity (Qs). An image
sensor having a high saturated signal electric charge quantity has
improved dynamic range and signal to noise (SN) ratio. Accordingly,
an increase of the saturated signal electric charge quantity is a
desirable property improvement of the image sensor. As a method of
increasing the saturated signal electric charge quantity, it is
conceivable that an area of the photodiode is increased, or that a
PN junction capacity of the photodiode is increased.
[0007] Patent Literature 1 suggests an image sensing device that
can provide high sensitivity by increasing a saturated signal
electric charge quantity without increasing an area of a
photoelectric conversion device and an impurity concentration.
CITATION LIST
Patent Literature
[0008] PTL 1: Japanese Patent Application Laid-open No.
2005-332925
SUMMARY OF INVENTION
Technical Problem
[0009] As described above, as the method of increasing the
saturated signal electric charge quantity, it is conceivable that
an area of the photodiode is increased, or a PN junction capacity
of the photodiode is increased.
[0010] However, if the area of the photodiode is increased, a total
pixel number in the image sensor may be undesirably decreased
because of the increase in the area of the photodiode at the same
angle of view. In addition, in order to increase the PN junction
capacity of the photodiode, the concentration in a P type region
and an N type region is increased, and as a result a dark current
is also increased. Therefore, there is a limit to increasing the PN
junction capacity.
[0011] Also, Patent Literature 1 shows a technology that a PN
junction capacity expansion part is elongated successively from a
surface side of a substrate to a depth direction of the substrate
to increase the saturated signal electric charge. However, an
arrangement of a readout electrode may be limited, or it may be
difficult to select a suitable pattern for a PN junction expansion
in order to give priority to readout signals.
[0012] In view of the circumstances as described above, it is
desired to increase a saturated signal electric charge
quantity.
Solution to Problem
[0013] According to an embodiment of the present technology, there
is provided an image sensing device (e.g., pixel in an imaging
device), including a first P type impurity region; a first N type
impurity region; and a capacity expansion part including a second P
type impurity region, a second N type impurity region, and a PN
junction surface, the second P type impurity region and the second
N type impurity region forming the PN junction surface, the first P
type impurity region, the first N type impurity region and the
capacity expansion part being disposed from an upper surface of a
semiconductor substrate in a depth direction.
[0014] The image sensing device further includes a readout
electrode that reads out an accumulated electric charge on one
surface opposite to the other surface of the first P type impurity
region closer to the second N type impurity region than the one
surface, in which the distance between the capacity expansion part
and the readout electrode is larger than the distance between the
capacity expansion part and the first N type impurity region.
[0015] The capacity expansion part may include second P type
impurity regions and second N type impurity regions, the second P
type impurity regions and the second N type impurity regions being
alternately disposed.
[0016] The semiconductor substrate may be made of silicon, and the
second P type impurity region may be formed of a material that
fills an interface with silicon with holes by a work function
difference.
[0017] The first P type impurity region and the second P type
impurity region may be layers disposed in different directions.
[0018] The first N type impurity region and the second N type
impurity region may be layers disposed in different directions.
[0019] The first N type impurity region may be configured of an N+
region having a high concentration and an N- region having a low
concentration.
[0020] The first N type impurity region may be the N- region having
a low concentration.
[0021] A potential gradient may be provided from the capacity
expansion part to the readout electrode for reading out the
electric charge.
[0022] The second N type impurity region in the capacity expansion
part may be formed square in a cross-section viewed from a
predetermined (or alternatively, desired) direction.
[0023] The second P type impurity region in the capacity expansion
part may be formed curve having a predetermined (or alternatively,
desired) width in a cross-section viewed from a predetermined (or
alternatively, desired) direction.
[0024] The second P type impurity region in the capacity expansion
part may be formed circle having a predetermined (or alternatively,
desired) width in a cross-section viewed from a predetermined (or
alternatively, desired) direction.
[0025] A repeat distance of the second P type impurity region and
the second N type impurity region in the capacity expansion part
may be 1 .mu.m or less.
[0026] A plurality of the image sensing devices may share a
floating diffusion, and the readout electrode may be disposed near
the floating diffusion.
[0027] The image sensing device according to an embodiment of the
present technology includes a first P type impurity region; a first
N type impurity region; and a capacity expansion part including a
second P type impurity region, a second N type impurity region, and
a PN junction surface, the second P type impurity region and the
second N type impurity region forming the PN junction surface, the
first P type impurity region, the first N type impurity region and
the capacity expansion part being disposed from an upper surface of
a semiconductor substrate in a depth direction.
Advantageous Effects of Invention
[0028] According to an embodiment of the present technology, a
saturated signal electric charge quantity can be increased.
[0029] It should be noted that the effect described here is not
necessarily limitative and may be any effect described in the
present technology.
BRIEF DESCRIPTION OF DRAWINGS
[0030] FIG. 1 is a view showing an example of a configuration of an
image sensing device.
[0031] FIG. 2 is a diagram showing a relationship between a depth
and a potential.
[0032] FIG. 3 is a view showing an example of a configuration of an
image sensing device.
[0033] FIG. 4 is a diagram showing a relationship between a depth
and a potential.
[0034] FIG. 5 is a view showing an example of a configuration of an
image sensing device.
[0035] FIG. 6 is a diagram showing a relationship between a depth
and a potential.
[0036] FIG. 7 is a view showing an example of a configuration of an
image sensing device.
[0037] FIG. 8 is a diagram showing a relationship between a depth
and a potential.
[0038] FIG. 9 is a view showing a configuration of an embodiment of
an image sensing device to which the present technology is
applied.
[0039] FIG. 10 is a view for explaining a flow of an electric
charge.
[0040] FIG. 11 is a cross-sectional view of an image sensing
device.
[0041] FIG. 12 is a view for explaining an arrangement of a readout
electrode.
[0042] FIG. 13 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0043] FIG. 14 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0044] FIG. 15 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0045] FIG. 16 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0046] FIG. 17 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0047] FIG. 18 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0048] FIG. 19 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0049] FIG. 20 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0050] FIG. 21 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0051] FIG. 22 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0052] FIG. 23 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0053] FIG. 24 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0054] FIG. 25 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0055] FIG. 26 is a view showing an example of a shape of an N+
region in a PN junction capacity expansion part.
[0056] FIG. 27 is a cross-sectional view of the image sensing
device shown in FIG. 1.
[0057] FIG. 28 is a view for explaining a size of 1 pixel.
[0058] FIG. 29 is a diagram for explaining a relationship between a
size of a pixel and a saturated signal electric charge
quantity.
[0059] FIG. 30 is a view for explaining a size of a pixel having a
PN junction capacity expansion part.
[0060] FIG. 31 is a diagram for explaining a relationship between a
size of a pixel and a saturated signal electric charge
quantity.
[0061] FIG. 32 is a view showing an example of a configuration of
another image sensing device.
[0062] FIG. 33 is a diagram showing a relationship between a depth
and a potential.
[0063] FIG. 34 is a view showing an example of a configuration of
still another image sensing device.
[0064] FIG. 35 is a view for explaining a structure shared by
pixels.
[0065] FIG. 36 is a view for explaining a structure shared by
pixels.
[0066] FIG. 37 is a view for explaining a structure shared by
pixels.
[0067] FIG. 38 is a diagram showing an example use of the image
sensing device.
[0068] FIG. 39 is a diagram showing a structure of the image
sensing apparatus.
DESCRIPTION OF EMBODIMENTS
[0069] Hereinafter, embodiments of the present technology will be
described with reference to the drawings.
[0070] The embodiments of the present technology will be described
in the following order.
[0071] 1. Structure of Image Sensing Device (Related Art)
[0072] 2. Structure of Image Sensing Device
[0073] 3. Shape of N+ Region in PN Junction Capacity Expansion
Part
[0074] 4. Improvement of Saturated Signal Electric Charge
Quantity
[0075] 5. Another structure of Image Sensing Device
[0076] 6. Sharing pixels
[0077] 7. Example Use of Image Sensing Device
[0078] The present technology described below is applicable to an
image sensing device, for example, a CCD image sensor or a CMOS
image sensor. Here, such an image sensing device will be described
as an example. By applying the present technology described below,
it can increase a saturated signal electric charge quantity (Qs)
that is a maximum value of a signal electric charge quantity
accumulated on the image sensing device (photoelectric conversion
device (photodiode)).
[0079] For describing the image sensing device to which the present
technology is applied providing the effect, an image sensing device
in the related art will be described briefly for comparison.
[0080] <Structure of Image Sensing Device (Related Art)>
[0081] FIG. 1 is a view showing an example of a configuration of an
image sensing device. An image sensing device or pixel 10 has a
structure where respective impurity regions, i.e., a P+ region 21,
an N+ region 22, an N- region 23, and a P+ region 24, are
se-quentially formed in a depth direction at an upper surface of a
silicon substrate, and P+ regions 25 are formed at side
surfaces.
[0082] In FIG. 1 and the following description, "+" and "-"
notations represent that an impurity concentration is higher or
lower than that in other regions.
[0083] Once light is incident on the image sensing device 10 having
such a structure, an electron-hole pair is generated, and a signal
electric charge (electron) is accumulated on junction parts of the
P type (or p-type) region and the N type (or n-type) region. A
readout electrode 31 for reading out the electric charge
accumulated is provided at an upper surface of the P+ region 21 in
the image sensing device 10 shown in FIG. 1.
[0084] FIG. 2 shows a relationship between a depth and a potential
in the image sensing device 10 having the structure shown in FIG.
1. In FIG. 2, a horizontal axis represents a depth from an upper
surface of the image sensing device 10 (an upper surface of the P+
region 21), and a vertical axis represents a negative potential. In
FIG. 2, the greater a value in the vertical axis (the lower the
negative potential) is, the greater a potential of an electron is,
and the lower a potential of a hole is.
[0085] In the following description, the image sensing device 10
having the structure shown in FIG. 1 and a potential status shown
in FIG. 2 is used as a reference. A difference from the image
sensing device 10 as a reference and a change in potential are
described.
[0086] FIG. 3, FIG. 5, and FIG. 7 each is a view showing an example
of an image sensing device in the related art having a structure
for increasing a saturated signal electric charge quantity (Qs)
with respect to the image sensing device 10 shown in FIG. 1. In the
following description, parts having a similar configuration of the
image sensing device 10 shown in FIG. 1 are denoted by the same
reference numerals, and thus detailed description thereof will be
hereinafter omitted.
[0087] An image sensing device or pixel 50 shown in FIG. 3 has a
structure that an N+ region 22 of the image sensing device 10 shown
in FIG. 1 is enlarged (deeper). An N+ region 61 of the image
sensing device 50 is provided deeper than the N+ region 22 of the
image sensing device 10 (FIG. 1).
[0088] FIG. 4 is a diagram showing a relationship between a depth
and a potential of the image sensing device 50 having the structure
shown in FIG. 3. In FIG. 4, a dotted line represents the potential
status of the image sensing device 10 shown in FIG. 2 by a solid
line, and a solid line represents a potential status of the image
sensing device 50.
[0089] As in the image sensing device 50, when the N+ region 61 is
deep, a potential in a deep part of bulk is deepened to add
capacity. As shown in FIG. 4, when the capacity is added, a status
that the negative potential is low (a peak status) can be
maintained in the depth direction, thereby increasing the saturated
signal electric charge quantity (Qs).
[0090] However, in this case, as an electric field in an image
sensor may be short or a barrier may be generated, and thus, all
signals may not be readout when a readout gate is turned on
(ON).
[0091] FIG. 5 is a view showing an another configuration of an
image sensing device. An image sensing device or pixel 100 shown in
FIG. 5 has a structure that the N+ region 22 of the image sensing
device 10 shown in FIG. 1 has a high impurity concentration. An N++
region 101 of the image sensing device 100 has an impurity
concentration higher than the N+ region 22 of the image sensing
device 10 (FIG. 1).
[0092] FIG. 6 is a diagram showing a relationship between a depth
and a potential of the image sensing device 100 having the
structure shown in FIG. 5. In FIG. 5, a dotted line represents the
potential status of the image sensing device 10 shown in FIG. 2 by
a solid line, and a solid line represents a potential status of the
image sensing device 100.
[0093] As in the image sensing device 100, when the N++ region 101
junctured with the P+ region 21 has the high impurity
concentration, the surface of the image sensor may be deeper, and a
capacity may be added to the surface. As shown in FIG. 6, when the
capacity is added, a status that the negative potential at a peak
may be higher, thereby increasing the saturated signal electric
charge quantity (Qs).
[0094] However, a readout voltage should be higher, thereby
generating a readout failure or degrading a white spot.
[0095] FIG. 7 is a view showing an example of a configuration of
another image sensing device. An image sensing device or pixel 150
shown in FIG. 7 has a structure where the P+ region 21 is thin
(shallow) and the N+ region 22 is thick (deep) of the image sensing
device 10 shown in FIG. 1 as a reference. A P+ region 151 of the
image sensing device 150 is thinner (shallower) than the P+ region
21 of the image sensing device 10 (FIG. 1), and a N+ region 152 of
the image sensing device 150 is thicker (deeper) than the N+ region
22 of the image sensing device 10 (FIG. 1).
[0096] FIG. 8 is a diagram showing a relationship between a depth
and a potential of the image sensing device 150 having the
structure shown in FIG. 7. In FIG. 8, a dotted line represents the
potential status of the image sensing device 10 shown in FIG. 2 by
a solid line, and a solid line represents a potential status of the
image sensing device 150.
[0097] As in the image sensing device 150, when the N+ region 152
is enlarged at a surface side of the silicon substrate, a depth at
a potential peak start may be shallower as shown in FIG. 8, thereby
increasing the saturated signal electric charge quantity (Qs).
[0098] However, similar to the image sensing device 100 shown in
FIG. 5, a surface electric field is increased, thereby degrading a
white spot.
[0099] An image sensing device according to at least one example
embodiment has a structure such that the saturated signal electric
charge quantity (Qs) may be increased, the white spot is not
degraded, and the readout failure is not generated.
[0100] <Configuration of Image Sensing Device>
[0101] FIG. 9 is a view showing a configuration of an embodiment of
an image sensing device to which the present technology is
applied.
[0102] In an image sensing device or pixel 300 shown in FIG. 9,
parts having a similar configuration of the image sensing device 10
shown in FIG. 1 are denoted by the same reference numerals, and
thus detailed description thereof will be hereinafter omitted. The
image sensing device 300 shown in FIG. 9 is different from the
image sensing device 10 shown in FIG. 1 in that the N- region 23 is
configured of an N- region 301, N+ regions 302-1, 302-2, and 302-3
(collectively referred to as 302), and P+ regions 303-1 and 303-2
(collectively referred to as 303), but is similar otherwise.
[0103] In the image sensing device 300, the N- region 301 having a
low concentration disposed as a lower layer of the N+ region 22
having a high concentration is shallow, a layer including N+
regions 302 and P+ regions 303 is formed between the N- region 301
and the P+ region 24 having a high concentration. Here, the layer
including the N+ regions 302 and the P+ regions is described as a
PN junction capacity expansion part 310. The PN junction capacity
expansion part 310 is disposed to enlarge a signal electric charge
accumulation part of the image sensing device 300, and therefore is
described here as the capacity expansion part.
[0104] The PN junction capacity expansion part 310 includes an N+
region 302-1, an N+ region 302-2, an N+ region 302-3, a P+ region
303-1, and a P+ region 303-2, a P+ region 303-1 is formed between
the N+ region 302-1 and the N+ region 302-2, a P+ region 303-2 is
formed between the N+ region 302-2 and the N+ region 302-3, in the
example shown in FIG. 9.
[0105] In this way, the PN junction capacity expansion part 310 has
a structure that the N+ regions 302 (N type impurity regions) and
the P+ regions 303 (P type impurity regions) are arranged
alternately.
[0106] A pitch distance of the PN junction capacity expansion part
310, i.e., a repeat distance of the N+ region 302 and the P+ region
303, may be, for example, preferably 1.0 .mu.m or less. A combined
width of the N+ region 302-1 and the P+ region 303-1 is 1.0 .mu.m
or less, for example. When the pitch distance is decreased to
minute, a concentration of N type impurities injected therein
increases, thereby further increasing the saturated signal electric
charge quantity (Qs).
[0107] As described later, the pitch distance of the PN junction
capacity expansion part 310 may be uniform as in the image sensing
device 300 shown in FIG. 9, but may be nonuniform in other
embodiments. Here, in one embodiment, the repeat distance of the N+
region 302 and the P+ region 303 is 1.0 .mu.m or less, for example.
However, it is not the description that limits an application scope
range of the present technology. The present technology may be
applicable to other distances. For example, even when the distance
is 1.0 .mu.m or more, the present technology is applicable.
[0108] When the N+ region 22 and the N- region 301 are considered
to be layers disposed in a vertical direction, the N+ regions 302
and the P+ regions 303 of the PN junction capacity expansion part
310 are disposed in a vertical direction. The PN junction capacity
expansion part 310 has a configuration that the N+ regions 302 and
the P+ regions 303 are laminated (or arranged) alternately in a
vertical direction, and are laminated in a direction different from
other layers. It should be understood that the impurity regions
(e.g., regions 22, 301, 302, 303, etc.) illustrated FIG. 9 are not
limited to the relative impurity concentrations and configurations
shown, but to illustrate example materials of the image sensing
device 300. Thus, throughout the instant description, N+ and/or N-
regions 22, 301 and/or 302 may be referred to as a first material
or N type regions while P+ and/or P- regions 21, 25, and/or 303 may
be referred to as a second material or P type regions. Furthermore,
it should be understood that example embodiments are not limited to
the first material being N type and the second material being P
type. For example, the first material may be a conductive material
while the second material may be an insulative material with a
conductivity that is less than the first material.
[0109] Also, the PN junction capacity expansion part 310 has a
potential gradient, as shown in FIG. 10. FIG. 10 is a view showing
the image sensing device or pixel 300 similar to FIG. 9, and shows
a flow of an electric charge by arrows in the image sensing device
300.
[0110] As shown by the arrows, the potential gradient is provided
so that an electric charge generated at the N+ region 302-1, an
electric charge generated at the N+ region 302-2, and an electric
charge generated at the N+ region 302-3 are moved to near the
readout electrode 31. In other words, the potential gradient is
provided between the PN junction capacity expansion part 310 and
the readout electrode 31 for reading out the electric charges.
[0111] FIGS. 11A-11C are top views of the image sensing device (or
pixel in an imaging device) 300 shown in FIG. 9. FIG. 11A is a
cross-sectional view of the image sensing device 300 similar to the
image sensing device 300 shown in FIG. 9. In the image sensing
device 300 shown in FIG. 11A, the PN junction capacity expansion
part 310 is similar to the PN junction capacity expansion part 310
of the image sensing device 300 shown in FIG. 9, an N type impurity
region 320 includes the N+ region 22 and the N- region 301, and a P
type impurity region 330 is the P+ region 21.
[0112] As shown FIG. 11A, in the image sensing device 300, the P
type impurity region 330, the N type impurity region 320, and the
PN junction capacity expansion part 310 are laminated from the side
where the readout electrode 31 is provided.
[0113] The P type impurity region 330 and the N type impurity
region 320 are layers laminated in a horizontal direction. The PN
junction capacity expansion part 310 is in a direction different
from the layer of the P type impurity region 330 and the layer of
the N type impurity region 320, and the N+ region 302 and the P+
region 303 are layers laminated in a vertical direction in FIG.
11A.
[0114] In this manner, the PN junction capacity expansion part 310
may be a layer laminated in a direction different from other
layers. The different direction may be a direction crossing
perpendicularly with other layers, or may be a direction (oblique
direction) crossing at a predetermined (or alternatively, desired)
angle.
[0115] FIG. 11B is a cross-sectional view of the image sensing
device 300 shown in FIG. 11A cutting along A-A'. FIG. 11C is a
cross-sectional view of the image sensing device 300 shown in FIG.
11A cutting along B-B'. That is to say, FIG. 11B is a
cross-sectional view of the N type impurity region 320, and FIG.
11C is a cross-sectional view of the PN junction capacity expansion
part 310.
[0116] As shown in FIG. 11B, in the cross-sectional view of the N
type impurity region 320, N type impurities are uniformly diffused.
In FIG. 11B, the readout electrode 31 is also shown for reference.
The readout electrode 31 is disposed to cover a part of the N type
impurity region 320. It should be understood that FIGS. 11B and 11C
are lateral cross sections of FIG. 11A. For example, FIG. 11C is a
first lateral cross section of FIG. 11A and FIG. 11B is a second
lateral cross section of FIG. 11A. However, the terms first and
second are used for the sake of convenience and do not limit
example embodiments. It should be further understood that the image
sensing device 300 may correspond to a pixel in an array of pixels
disposed in a substrate of an imaging device (not labeled). As
shown in FIG. 9 and FIG. 11A, the pixel includes a first material
(e.g., N type impurity regions 22, 301, 302, and 320) disposed in
the substrate, and a second material (e.g., P type impurity regions
302 and 330) disposed in the substrate. Further, as shown in FIG.
11A, a first region of the first material (e.g., leftmost branch of
N type impurity region in PN junction capacity expansion part 310),
a second region of the first material (e.g., branch of N-type
impurity region in PN junction capacity expansion part 310
immediately adjacent to the leftmost branch), and a third region of
the second material (e.g., form at least one junction (e.g., a PN
junction). Further, as shown in FIG. 11C, the first lateral cross
section of the substrate intersects the at least one junction
(i.e., intersects the regions 302 and 303). A second lateral cross
section (e.g., FIG. 11B) of the substrate intersects at least one
fourth region of the first material (e.g., N type impurity region
320). As shown in FIGS. 11B and 11C, the at least one fourth region
of the first material (e.g., N-type impurity region 320 in FIG.
11B) occupies a different amount (e.g., greater amount) of surface
area in the second lateral cross section in FIG. 11B than the first
region of the first material and the second region of the first
material occupy in the first lateral cross section in FIG. 11C.
That is, the N-type impurity region 320 in FIG. 11B occupies a
different amount (e.g., a greater amount) of surface area than the
N-type impurity region in FIG. 11C (illustrated as N+ regions 302).
It should be further understood that the first lateral cross
section (e.g., FIG. 11C) is taken closer to a light incident side
of the image sensing device 300 (or first pixel) than the second
lateral cross section (e.g., FIG. 11B). As illustrated in FIGS.
11A-11C, the first material is an N type material and the second
material is a P type material. However, example embodiments are not
limited thereto. According to at least one other embodiment, the
first material is a conductive material (e.g., N type material) and
the second material is an insulating material (see, for example,
FIG. 34). It should be appreciated from FIGS. 11A-11C that the
first material (e.g., N type material) looks like a single region
from the perspective of the readout electrode 31 (see FIG. 11B),
and looks like multiple regions or multiple junctions from the
perspective of a light incident side of the image sensing device
300 (see FIG. 11C). This increases the saturated signal electric
charge quantity while allowing for the readout electrode 31 to
disposed at various positions (see FIG. 12).
[0117] In the image sensing device 300 to which the present
technology is applied, a position of the readout electrode 31 is
not limited, and may be disposed at various positions shown in FIG.
12. Referring to FIG. 12, a readout electrode 31-1 may be provided
at the N type impurity region 320 in a right side in FIG. 12
similar to FIG. 11B. Alternatively, a readout electrode 31-2 may be
provided at the N type impurity region 320 in a lower side in FIG.
12 as shown in FIG. 12.
[0118] The readout electrode, i.e., the readout electrode 31-1 or
the readout electrode 31-2 as shown, has high degree of freedom not
only in the position, but also in the size. The present technology
may be applied to the readout electrode having any size. In
addition, as shown in FIG. 12, a readout electrode 31-3 may be
provided at a corner of the N type impurity region 320.
Furthermore, as shown in FIG. 12, a readout electrode 31-4 may be
provided at a center of the N type impurity region 320.
[0119] The readout electrode 31 is disposed at any position of the
readout electrodes 31-1 to 31-4. Note that the readout electrode 31
may be disposed at a position other than the positions shown in
FIG. 12.
[0120] According to the present technology, the structure for
increasing the saturated signal electric charge quantity (Qs) is
disposed not at near the surface of the substrate as in the image
sensing device described referring to FIG. 3 to FIG. 8, but at the
back side of the substrate. The readout electrode 31 disposed at
the surface of the substrate can be at a desirable position without
limitation, as described above. That is to say, as the PN junction
capacity expansion part 310 does not affect thereon, the readout
electrode 31 has no limitation.
[0121] FIG. 11C is a cross-sectional view of the PN junction
capacity expansion part 310. In the cross-section of the PN
junction capacity expansion part 310, the N+ regions 302 and the P+
regions 303 are disposed alternately. The N+ regions 302 of the PN
junction capacity expansion part 310 are disposed in a lattice and
are dispersed as 16 squares in the embodiment shown in FIG.
11C.
[0122] One square may have any size, and desirably, for example,
1.0 .mu.m or less (a combined size of the N type region and the P
type region adjacent in the square is 1.0 .mu.m or less) as
described above. Although the shape is square here, a four-sided
square, a rectangle, a rhombus, a trapezoidal, or any shape such as
a circle and an oval other than the square may be possible.
[0123] <Shape of N+ Region in PN Junction Capacity Expansion
Part>
[0124] Here, referring to FIG. 13 to FIG. 26, the shape of the N+
region 302 in the PN junction capacity expansion part 310 will be
further described. FIG. 13 to FIG. 26 each shows a cross-sectional
view of the PN junction capacity expansion part 310 similar to FIG.
11C. Also, FIG. 13 to FIG. 26 each shows the readout electrode 31
for explanation.
[0125] The shape of the N+ region 302 in the PN junction capacity
expansion part 310 is described as an example. If the shape of the
P+ region 303 in the PN junction capacity expansion part 310 is
described as an example, it is basically similar. Here, the N+
region 302 is described as an example.
[0126] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 13 are disposed in a lattice same as the N+
regions 302 shown in FIG. 11C, but are dispersed as 28 squares
where one square is small. In addition, the respective N+ regions
302 are formed so that corners are in contact therewith. In this
manner, the shapes of the N+ regions 302 in the PN junction
capacity expansion part 310 may be in the lattice, and one lattice
may be formed small. As shown in FIG. 13, the first material (e.g.,
N+ regions 302) and the second material (e.g., regions 303) are in
a checkered pattern. For example, wherein the first material (e.g.,
regions 302) forms a grid of n columns and m rows in the second
material.
[0127] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 14 are disposed in a lattice same as the N+
regions 302 shown in FIG. 11C, but are dispersed as 4 squares where
one square is large. In this manner, the shapes of the N+ regions
302 in the PN junction capacity expansion part 310 may be in the
lattice, and one lattice may be formed large.
[0128] As described above, when the N+ regions 302 of the PN
junction capacity expansion part 310 shown in FIG. 14 are applied
under the condition that the pitch distance of the PN junction
capacity expansion part 310 is preferably 1.0 .mu.m or less, the N+
regions 302 can be provided in a state that the condition is
satisfied as long as one pixel is small. That is to say, the size
of the N+ regions 302 in the PN junction capacity expansion part
310 may be set depending on the size of one pixel.
[0129] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 15 are disposed in a lattice same as the N+
regions 302 shown in FIG. 11C, but the N+ region 302 disposed at
the readout electrode 31 is greater than the N+ regions 302 at
other regions. In this manner, the shapes and the sizes of the
respective N+ regions 302 in the PN junction capacity expansion
part 310 may be not the same.
[0130] The P+ regions 303 of the PN junction capacity expansion
part 310 shown in FIG. 16 are formed discretely in a lattice and
the N+ regions 302 fill the space between the P+ regions 303. The
N+ regions 302 are connected excluding the P+ regions 303. That is,
the second material (e.g., regions 303) forms a grid of n columns
and m rows in the first material (e.g., regions 302). As shown in
FIG. 16, the N+ regions 302 are not be formed as those shown in
FIG. 15, i.e., the N+ regions 302 are formed apart with no
connections.
[0131] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 17 are similar to the N+ regions 302 shown
in FIG. 16, but the N+ region 302 disposed at the readout electrode
31 is greater than the N+ regions 302 at other regions, and no P+
regions 303 are provided at the readout electrode 31.
[0132] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 18 are formed rectangular such that long
sides of the rectangle are in parallel with the readout electrode
31.
[0133] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 19 are formed rectangular similar to the N+
regions 302 shown in FIG. 18, but are different from those in
respect to the directions. The N+ regions 302 shown in FIG. 19 are
formed rectangular such that long sides of the rectangle are
orthogonal to the readout electrode 31.
[0134] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 20 are formed rectangular similar to the N+
regions 302 shown in FIG. 19, but are different from those in
respect to the sizes. The N+ regions 302 shown in FIG. 20 are
formed rectangular such that long sides of the rectangle are
orthogonal to the readout electrode 31. Between the N+ regions 302,
the P+ regions 303 are provided.
[0135] As shown in FIG. 18 to FIG. 20, the shape of the N+ regions
302 may be rectangular, and the long sides of the rectangle may be
in parallel with or orthogonal to the readout electrode 31. That
is, the first material (e.g., N+ regions 302) and the second
material (e.g., P+ regions 303) have linear shapes in the first
lateral cross section.
[0136] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 21 fill the regions excluding the P+ regions
303 each provided in a straight line to an oblique direction with a
predetermined (or alternatively, desired) width within the PN
junction capacity expansion part 310.
[0137] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 22 fill the regions excluding the P+ regions
303 each provided in a curved shape (partly in a straight line)
with a predetermined (or alternatively, desired) width within the
PN junction capacity expansion part 310.
[0138] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 23 are provided further excluding the P+
regions 303 each provided in a straight line to oblique and
horizontal directions with a predetermined (or alternatively,
desired) width from the N+ regions 302 shown in FIG. 22.
[0139] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 24 fill the regions excluding the P+ regions
303 each provided in a wavy shape (curved shape) with a
predetermined (or alternatively, desired) width within the PN
junction capacity expansion part 310.
[0140] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 25 fill the regions excluding the P+ regions
303 each provided in a circle with a predetermined (or
alternatively, desired) width within the PN junction capacity
expansion part 310.
[0141] The N+ regions 302 of the PN junction capacity expansion
part 310 shown in FIG. 26 fill the regions excluding the P+ regions
303 each provided in a spiral shape with a predetermined (or
alternatively, desired) width within the PN junction capacity
expansion part 310.
[0142] As above, the shapes of the N+ regions 302 in the PN
junction capacity expansion part 310 (the shapes of the P+ regions
303 in the PN junction capacity expansion part 310) may be a
variety of shapes including a lattice, a bar and a curve. Also, it
may be line symmetry, point symmetry, or asymmetry.
[0143] Note that the shapes shown FIG. 11C, FIG. 13 to FIG. 26 are
illustrative, not limitative, and may be other shapes to which the
present technology is applicable.
[0144] However, the shape may preferably satisfy the conditions as
described below. As described above, the pitch distance of the PN
junction capacity expansion part 310 is 1.0 .mu.m or less. In
addition, a ratio of the N+ regions 302 and the P+ regions 303 is
equivalent (1:1) or the number of the N+ regions 302 may be
slightly greater than that of the P+ regions 303 within the PN
junction capacity expansion part 310.
[0145] In the following description, the structure of the PN
junction capacity expansion part 310 shown in FIG. 11C will be
described as an example.
[0146] <Improvement of Saturated Signal Electric Charge
Quantity>
[0147] As described above, in the image sensing device 300, the P
type impurity region 330, the N type impurity region 320 and the PN
junction capacity expansion part 310 are laminated, thereby
improving the saturated signal electric charge quantity. Here, the
improvement of the saturated signal electric charge quantity will
be further described.
[0148] FIGS. 27A-27C show again the configuration of the image
sensing device or pixel 10 shown in FIG. 1 as a reference (the
image sensing device shown for comparing with the image sensing
device or pixel 300 to which the present technology is applied).
For comparing with the image sensing device 300 shown in FIGS.
11A-11C, FIG. 27A shows a cross-sectional view of a side of the
image sensing device 10, FIG. 27B shows a cross-sectional view of
the image sensing device 10 shown in FIG. 27A cut along A-A', and
FIG. 27C shows a cross-sectional view of the image sensing device
10 shown in FIG. 27A cut along B-B'. For reference, the readout
electrode 31 is also shown in FIG. 27B.
[0149] FIG. 27A is a cross-sectional view of the image sensing
device 10 similar to that shown in FIG. 1. In the image sensing
device 10 shown in the FIG. 27A, the P+ region 21 of the image
sensing device 10 shown in FIG. 1 is described as a P type impurity
region 410, and the N+ region 22 and the N- region 23 are
collectively described as the N type impurity region 420.
[0150] As the image sensing device 10 has no region corresponding
to the PN junction capacity expansion part 310, the P type impurity
region 410 and the N type impurity region 420 are laminated as
shown in FIG. 27A.
[0151] FIG. 27B is a cross-sectional view of the image sensing
device 10 shown in FIG. 27A cut along A-A', and FIG. 27C is a
cross-sectional view cut along B-B'. As to the image sensing device
10, FIG. 27B and FIG. 27C are cross-sectional views cut at
different positions in the N type impurity region 420.
[0152] That is to say, as shown in FIG. 27B and FIG. 27C, N-type
impurities are diffused uniformly in the cross section in the N
type impurity region 420. Thus, the N-type impurity region 420
occupies a same amount of surface area in both cross sections shown
in FIGS. 27B and 27C.
[0153] A relationship between the size of the image sensing device
10 and the saturated signal electric charge quantity will be
described referring to FIGS. 28A-28C and FIG. 29.
[0154] FIGS. 28A-28C are top views of the image sensing device 10
cut along A-A' or B-B' in FIG. 27B or FIG. 27C. FIGS. 28A-28C
include 1 pixel, 4 pixels and 16 pixels in a 4 .mu.m.times.4 .mu.m,
and each pixel has the configuration of the image sensing device 10
shown in FIG. 1 (FIGS. 27A-27C).
[0155] As the image sensing device 10 shown in FIG. 28A includes 1
pixel within 4 .mu.m.times.4 .mu.m, 1 pixel has a size of 4
.mu.m.times.4 .mu.m. Hereinafter, the image sensing device 10
having a size of 4 .mu.m.times.4 .mu.m is in a status "A".
[0156] As the image sensing device 10 shown in FIG. 28B includes 4
pixels within 4 .mu.m.times.4 .mu.m, 1 pixel has a size of 2
.mu.m.times.2 .mu.m. Hereinafter, the image sensing device 10
having a size of 2 .mu.m.times.2 .mu.m is in a status "B". As the
image sensing device 10 shown in FIG. 28C includes 16 pixels within
4 .mu.m.times.4 .mu.m, 1 pixel has a size of 1 .mu.m.times.1 .mu.m.
Hereinafter, the image sensing device 10 having a size of 1
.mu.m.times.1 .mu.m is in a status
[0157] FIG. 29 is a graph showing a change of saturation when the
same potential is achieved in the image sensing device 10 in the
status "A", the status "B", and the status "C". In the graph shown
in FIG. 29, a horizontal axis represents a minimum unit cell size
(size of 1 pixel) and a vertical axis represents the saturated
signal electric charge quantity per unit area. In the graph shown
in FIG. 29, the saturated signal electric charge quantities per
unit area in the status "A", the status "B", and the status "C" are
shown by points (circled A, B and C are attached in the
figure).
[0158] When the saturated signal electric charge quantity per unit
area in the status "A" of the image sensing device 10 is compared
with the saturated signal electric charge quantity per unit area in
the status "B" of the image sensing device 10, the saturated signal
electric charge quantity per unit area in the status "A" is greater
than the saturated signal electric charge quantity per unit area in
the status "B". When the saturated signal electric charge quantity
per unit area in the status "A" of the image sensing device 10 is
compared with the saturated signal electric charge quantity per
unit area in the status "C" of the image sensing device 10, the
saturated signal electric charge quantity per unit area in the
status "A" is greater than the saturated signal electric charge
quantity per unit area in the status "C". When the saturated signal
electric charge quantity per unit area in the status "B" of the
image sensing device 10 is compared with the saturated signal
electric charge quantity per unit area in the status "C" of the
image sensing device 10, the saturated signal electric charge
quantity per unit area in the status "B" is greater than the
saturated signal electric charge quantity per unit area in the
status "C".
[0159] The change from the status "A" to the status "B" is that the
pixel size becomes small, and the PN junction capacity is
increased. Along with this change, the area of the P type impurity
regions increases, and the area of the N type impurity regions
relatively decreases. The effect is that the saturated signal
electric charge quantity per unit area may be decreased. The change
from the status "B" to the status "C" is that the pixel size
becomes smaller. Along with this change, the area of the N type
impurity regions decreases, and the N junction capacity increases.
The effect is that the saturated signal electric charge quantity
per unit area may be increased.
[0160] From the above relationship, it should be understood that as
the pixel size becomes minute, the saturated signal electric charge
quantity per unit area may tend to increase. If the pixel size is
not minute at a suitable size, the saturated signal electric charge
quantity per unit area may not increase.
[0161] Specifically, when the pixel size is 1.0 .mu.m or less, the
saturated signal electric charge quantity per unit area can
increase. As described above, the pitch distance of the PN junction
capacity expansion part 310 of the image sensing device 300 to
which the present technology is applied is 1.0 .mu.m or less as an
example.
[0162] When the size of the image sensing device 300 to which the
present technology is 4 .mu.m.times.4 .mu.m, the configuration will
be shown in FIGS. 30A and 30B. FIG. 30A is similar FIG. 11B, and is
a cross-sectional view that the image sensing device 300 shown in
FIG. 11A is cut along A-A'. FIG. 30B shows a cross-sectional view
of the image sensing device 300 shown in FIG. 11A cut along B-B'.
For reference, the readout electrode 31 is also shown in FIG.
30A.
[0163] The image sensing device 300 shown in FIG. 30A is a cross
section (e.g., lateral cross section) of the N type impurity region
320, and includes 1 pixel N type impurity region 320 within 4
.mu.m.times.4 .mu.m. The N type impurity region 320 having the size
of 4 .mu.m.times.4 .mu.m is in a status "D".
[0164] The image sensing device 300 shown in FIG. 30B is a cross
section (e.g., lateral cross section) of the PN junction capacity
expansion part 310, and includes 1 .mu.m.times.1 .mu.m (accurately,
1 .mu.m.times.1 .mu.m or less) 16 N+ regions 302 within 4
.mu.m.times.4 .mu.m. The state that 1 .mu.m.times.1 .mu.m 16 N+
regions 302 are formed within 4 .mu.m.times.4 .mu.m in a status
"E".
[0165] The image sensing device 300 has the N type impurity region
320 in the status "D" at a readout electrode 31 side, and the PN
junction capacity expansion part 310 in the status "E" far from the
readout electrode 31 (at a deep substrate). Specifically, the image
sensing device 100 has a configuration that different statuses "D"
and "E" in 1 pixel.
[0166] The status "D" (FIG. 30A) is same as the status "A" in FIG.
28A, and the status "E" (FIG. 30B) is same as the status "C" in
FIG. 28C. The image sensing device 300 has a configuration
equivalent to 1 pixel near the readout electrode 31 (e.g., in FIG.
30A), and a configuration equivalent to multiple minute pixels far
therefrom (e.g., in FIG. 30B).
[0167] FIG. 31 is a graph showing a change of saturation when the
same potential is achieved in the image sensing device 10 in the
status "A", the status "B", and the status "C" to which the
saturated signal electric charge quantity per unit area of the
image sensing device 300 is added.
[0168] The image sensing device 300 includes a pixel in the status
"D" in FIG. 30A, and functions as 1 pixel having a size of 4
.mu.m.times.4 .mu.m. FIG. 31 shows the saturated signal electric
charge quantity per unit area in the status "D".
[0169] Referring to FIG. 31, the image sensing device 300 has the
size similar to that of the image sensing device 10 in the status
"A", but the saturated signal electric charge quantity per unit
area is similar to that of the image sensing device 10 in the
status "C" as shown by status "D". Thus, according to the image
sensing device 300, the saturated signal electric charge quantity
can be remarkably increased (e.g., from status "A" to status "D")
as compared with the image sensing device having the same size to
which the present technology is not applied in FIGS. 28A and
28B.
[0170] <Another Structure of Image Sensing Device>
[0171] Another structure of the image sensing device will be
described.
[0172] FIG. 32 is a view showing a configuration of another image
sensing device to which the present technology is applied. A basic
configuration of an image sensing device or pixel 500 shown in FIG.
32 is similar to that of the image sensing device 300 shown in FIG.
9, but is different in that no N+ region 22 is provided, and the N
type impurity region is configured only of an N- region 501. In the
image sensing device 500, the concentration of the N type impurity
at the readout electrode 31 side is low. Also, in the image sensing
device 500, the PN junction capacity expansion part 310 is disposed
deeper than the N- region 501.
[0173] In this manner, when the concentration of the N type
impurity at the readout electrode 31 side is low, the potential can
be shallow. FIG. 33 is a diagram showing a relationship between a
depth and a potential of the image sensing device 500 having the
structure shown in FIG. 32. In FIG. 33, a dotted line represents
the potential status of the image sensing device 10 shown in FIG. 2
by a solid line, and a solid line represents a potential status of
the image sensing device 500.
[0174] When the concentration of the N type impurity at the readout
electrode 31 side is low in the image sensing device 500, a depth
at a potential peak start can be shallow as shown in FIG. 33.
[0175] In addition, as the image sensing device 500 has the PN
junction capacity expansion part 310, the saturated signal electric
charge quantity can be increased similar to the image sensing
device 300.
[0176] The PN junction capacity expansion part 310 is disposed at a
substrate side far from the readout electrode 31, thereby improving
the saturated signal electric charge quantity. For example, when it
is enough that the saturated signal electric charge quantity same
as that in the related art, i.e., the saturated signal electric
charge quantity provided by the image sensing device 10 shown in
FIG. 1, is acquired, the potential is made to be shallow at the
surface side of the substrate as in the image sensing device 500
shown in FIG. 32, thereby alleviating a surface electric field and
improving a white spot.
[0177] By shallowing the potential, a readout capability of the
readout electrode 31 can be improved, and the electric charge
generated can be accurately readout. Furthermore, by shallowing the
potential, a readout voltage can be decreased, thereby decreasing a
power consumption.
[0178] FIG. 34 is a view showing a configuration of still another
image sensing device to which the present technology is applied. A
configuration of an image sensing device 600 shown in FIG. 34 is
same as that of the image sensing device 300 shown in FIG. 9, but
is different in terms of a material of the PN junction capacity
expansion part 310 (FIG. 9).
[0179] A PN junction capacity expansion part 610 of the image
sensing device 600 shown in FIG. 34 includes N+ regions 302 and P+
equivalent regions 601. The P+ equivalent regions 601 are regions
equivalent to the P+ regions 303 PN of the junction capacity
expansion part 310 in the image sensing device 300 shown in FIG. 9.
The P+ equivalent regions 601 is filled with a material used as an
insulation film, e.g., an oxide film, other than the
impurities.
[0180] The material that fills the P+ equivalent region 601 may be
any material that can fill an interface with silicon with holes by
the work function when the image sensing device or pixel 600 is
configured of a silicon substrate.
[0181] The P+ equivalent regions 601 are formed by forming grooves
using a technique such as etching at the time of the production of
the image sensing device 600, and filling the grooves with a
material used as an insulation film, e.g., an oxide film.
[0182] When the P+ equivalent regions 601 are formed using a
technique such as etching, P+ regions 24 are formed, the P+ regions
24 are grooved to the N- region 301 to form grooves, and the
grooves are filed with the material for forming the P+ equivalent
regions 601. When the P+ equivalent regions 601 are thus formed, as
shown in FIG. 34, the P+ equivalent regions 601 are also formed in
the P+ regions 24.
[0183] <Sharing Pixels>
[0184] In the above-described embodiments, one image sensing device
is illustrated and described. For example, the image sensing
devices or pixels 300 are disposed on a pixel array unit in a
two-dimensional m.times.n array. When a plurality of the image
sensing devices 300 are disposed, a plurality of pixels, e.g., 2
pixels or 4 pixels may share a floating diffusion (FD) (or charge
accumulation region). In the image sensing device to which the
present technology is applied, a multi-pixel sharing technology is
applicable.
[0185] FIGS. 35A and 35B show image sensing devices each including
4 pixels disposed on a pixel array unit in a horizontal direction.
FIG. 35A shows that the image sensing devices 300 shown in FIG. 9
(FIG. 11A) each includes 4 pixels in a horizontal direction. On
each of the image sensing devices 300-1 to 300-4, readout
electrodes 31-1 to 31-4 are disposed at surface sides of
substrates, and PN junction capacity expansion parts 310-1 and
310-4 are disposed at deep sides of the substrates.
[0186] FIG. 35B shows that the image sensing devices 600 shown in
FIG. 34 each includes 4 pixels in a horizontal direction. On each
of the image sensing devices 600-1 to 600-4, readout electrodes
31-1 to 31-4 are disposed at surface sides of the substrates, and
PN junction capacity expansion parts 610-1 and 610-4 are disposed
at deep sides of the substrates.
[0187] In the image sensing devices 300 and the image sensing
devices 600 shown in FIGS. 35A and 35B (hereinafter, the
description is continued by illustrating the image sensing devices
300), the readout electrodes 31 of adjacent image sensing devices
300 are disposed adjacent.
[0188] For example, the readout electrode 31-1 and the readout
electrode 31-2 of the image sensing device 300-1 and the image
sensing device 300-2 adjacent are disposed adjacent. Similarly, the
readout electrode 31-3 and the readout electrode 31-4 of the image
sensing device 300-3 and the image sensing device 300-4 adjacent
are disposed adjacent.
[0189] The image sensing device 300-1 and the image sensing device
300-2 disposed adjacent share one floating diffusion (FD) 701-1.
Similarly, the image sensing device 300-3 and the image sensing
device 300-4 disposed adjacent share one floating diffusion (FD)
701-2.
[0190] The floating diffusion 701-1 is disposed between the readout
electrode 31-1 and the readout electrode 31-2. The floating
diffusion 701-1 is disposed over a P type impurity region 330-1 and
a P type impurity region 330-2. In FIG. 35A, there is a line
between the P type impurity region 330-1 and the P type impurity
region 330-2 to clarify a boundary. The line is added for
description, there is no such a line between the type impurity
region 330-1 and P type impurity region 330-2.
[0191] Similarly, a floating diffusion 701-2 is disposed between
the readout electrode 31-3 and the readout electrode 31-4. The
floating diffusion 701-2 is disposed over a P type impurity region
330-3 and a P type impurity region 330-4. In view of FIGS. 35A and
35B, it may be said that a first pixel (e.g., image sensing device
300-1) and a second pixel (e.g., image sensing device 300-2) are
adjacent to one another and the floating diffusion (or the charge
accumulation region) 701-1 is between a first electrode (e.g.,
readout electrode 31-1) and a second electrode (e.g., readout
electrode 31-2).
[0192] FIG. 36 is a top view of the image sensing device 300 shown
in FIG. 35A, and a cross-sectional view of a part of the PN
junction capacity expansion part 310. For description, the readout
electrode 31 is also shown. FIG. 36 shows the image sensing device
300 including 2.times.2=4 pixels.
[0193] The image sensing device 300-1 (PN junction capacity
expansion part 310-1) and the image sensing device 300-2 (PN
junction capacity expansion part 310-2) are adjacent in a
horizontal direction, the 2 pixels share one floating diffusion
(FD) (or charge accumulation region) 701-1. The floating diffusion
701-1 is disposed between the readout electrode 31-1 of the image
sensing device 300-1 and the readout electrode 31-2 of the image
sensing device 300-2.
[0194] Similarly, the image sensing device 300-11 (PN junction
capacity expansion part 310-11) and the image sensing device 300-12
(PN junction capacity expansion part 310-12) are adjacent in a
horizontal direction, and 2 pixels share one floating diffusion
701-11. The floating diffusion 701-11 is disposed between the
readout electrode 31-11 of the image sensing device 300-11 and the
readout electrode 31-12 of the image sensing device 300-12.
[0195] In this manner, 2 pixels adjacent can share one floating
diffusion 701.
[0196] 4 pixels can share one floating diffusion 701. FIG. 37 shows
the image sensing device 300 where 4 pixels share one floating
diffusion 701.
[0197] FIG. 37 shows the image sensing device 300 including
2.times.2, 4 pixels same as in FIG. 36. 4 pixels share one floating
diffusion 701. As shown in FIG. 37, the floating diffusion 701 is
disposed at a center of 4 pixels.
[0198] Surrounding the floating diffusion 701, the readout
electrode 31-1 of the image sensing device 300-1 (PN junction
capacity expansion part 310-1), the readout electrode 31-2 of the
image sensing device 300-2 (PN junction capacity expansion part
310-2), the readout electrode 31-11 of the image sensing device
300-11 (PN junction capacity expansion part 310-11), and the
readout electrode 31-12 of the image sensing device 300-12 (PN
junction capacity expansion part 310-12) are disposed.
[0199] In this manner, 4 pixels adjacent can share one floating
diffusion 701. In other words, a first pixel (e.g., image sensing
device 310-1), a second pixel (e.g., image sensing device 310-2), a
third pixel (e.g., image sensing device 310-11) and a fourth pixel
(e.g., image sensing device 310-12) are in a 2.times.2 matrix, and
the charge accumulation region 701 is at a center portion of the
2.times.2 matrix. Further, the charge accumulation region 701 is
surrounded by a first electrode (e.g., readout electrode 31-1), a
second electrode (e.g., readout electrode 31-2), a third electrode
(e.g., readout electrode 31-11) and a fourth electrode (e.g.,
readout electrode 31-12).
[0200] According to the present technology, as described above, the
readout electrode 31 has high degree of freedom as to the position.
When 2 pixels or 4 pixels share one floating diffusion 701, the
readout electrode 31 can be disposed at an appropriate position, as
described above.
[0201] According to the present technology, the saturated signal
electric charge quantity in the image sensing device can be
improved, as described above. Furthermore, even when it is
configured such that the saturated signal electric charge quantity
is improved, the size of the image sensing device is not increased
compared to related art devices.
[0202] <Use Example of Image Sensing Device>
[0203] FIG. 38 is a diagram showing example uses of the image
sensing device described above.
[0204] The image sensing device or apparatus described above can be
used in a variety of cases where light such as visible rays,
infrared rays, ultraviolet rays, and X rays is sensed, for example,
as described below:
[0205] An imaging apparatus according to at least one embodiment
may be used for viewing and may include a digital camera and/or a
portable device having a camera. An imaging apparatus according to
at least one embodiment may be used for traffic and may include a
vehicle-mounted sensor for imaging a front, a back, surroundings
and inside of a vehicle for the purpose of a safety drive of an
automatic stop or identification of a driver's status. An imaging
apparatus according to at least one embodiment may be used as a
monitoring camera for monitoring a running vehicle and a road, and
a distance finding sensor for measuring a distance between
vehicles. An imaging apparatus according to at least one embodiment
may be used in consumer electrical appliances including a TV, a
refrigerator, and an air conditioner for the purpose of appliance
operation by a user's gesture imaged. An imaging apparatus
according to at least one embodiment may be used in a health care
or medical apparatus including an endoscope and an angiography by
receiving infrared rays. An imaging apparatus according to at least
one embodiment may be used in a security apparatus including a
security monitoring camera and a personal authentication camera. An
imaging apparatus according to at least one embodiment may be used
in a beauty apparatus including a skin diagnosis apparatus and a
scalp microscope. An imaging apparatus according to at least one
embodiment may be used in a sports apparatus including an action
camera and a wearable camera for use in sports. An imaging
apparatus according to at least one embodiment may be used in an
agricultural apparatus including a camera for monitoring a field
and crop status.
[0206] FIG. 39 is a block diagram showing a configuration example
of an image sensing apparatus (camera apparatus) 1000 as an example
of an electronic device to which the present technology is
applied.
[0207] As shown in FIG. 39, the image sensing apparatus or imaging
apparatus 1000 includes an optical system having a lens group 1001,
an image sensing device 1002 in an imaging device, a camera signal
processing unit DSP 1003, a frame memory 1004, a display 1005, a
recording unit 1006, an operation unit 1007, and a power source
1008. The DSP 1003, the frame memory 1004, the display 1005, the
recording unit 1006, the operation unit 1007, and the power source
1008 are mutually connected via a bus line 1009.
[0208] The lens group 1001 takes an incident light (imaging light)
from an object to be imaged, and images on an imaging surface of
the image sensing device 1002. The image sensing device 1002
converts an amount of incident light imaged on the imaging surface
by the lens group 1001 into an electrical signal per pixel to
output a pixel signal.
[0209] The display 1005 is configured of a panel display such as a
liquid crystal display and an organic electro luminescence (EL)
display, and displays video or a still picture imaged by the image
sensing device 1002. The recording unit 1006 records the video or
the still picture imaged by the image sensing device 1002 into a
recording medium such as a memory card, a video tape and a DVD
(Digital Versatile Disk).
[0210] The operation unit 1007 issues an operation command to a
variety of functions of the image sensing apparatus 1000 under a
user's operation. The power source 1008 provides appropriately a
target to be supplied with a variety of power supplies for
operation of the DSP s1003, the frame memory 1004, the display
1005, the recording unit 1006, and the operation unit 1007.
[0211] The image sensing apparatus 1000 is applied to a video
camera, a digital still camera, and a camera module for a mobile
device such as a smart phone and a portable phone. In the image
sensing apparatus 1000, the image sensing device according to the
above-described embodiments can be used as the image sensing device
1002. In this manner, an image quality of the image sensing
apparatus 1000 can be improved.
[0212] In the present specification, the system represents a whole
apparatus configured of a plurality of apparatuses.
[0213] It should be noted that the effect described here is only
illustrative and not limited, and other effects may be
provided.
[0214] The embodiments of the present technology are not limited to
the above-described embodiments, and variations and modifications
may be made without departing from the scope of the present
technology.
[0215] The present technology may have the following
configurations.
(1) An image sensing device, including: a first P type impurity
region; a first N type impurity region; and a capacity expansion
part including a second P type impurity region, a second N type
impurity region, and a PN junction surface, the second P type
impurity region and the second N type impurity region forming the
PN junction surface, the first P type impurity region, the first N
type impurity region and the capacity expansion part being disposed
from an upper surface of a semiconductor substrate in a depth
direction. (2) The image sensing device according to (1) above,
further including: a readout electrode that reads out an
accumulated electric charge on one surface opposite to the other
surface of the first P type impurity region closer to the second N
type impurity region than the one surface, in which the distance
between the capacity expansion part and the readout electrode is
larger than the distance between the capacity expansion part and
the first N type impurity region. (3) The image sensing device
according to (1) or (2) above, in which the capacity expansion part
includes second P type impurity regions and second N type impurity
regions, the second P type impurity regions and the second N type
impurity regions being alternately disposed. (4) The image sensing
device according to any one of (1) to (3) above, in which the
semiconductor substrate is made of silicon, and the second P type
impurity region is formed of a material that fills an interface
with silicon with holes by a work function difference. (5) The
image sensing device according to any one of (1) to (4) above, in
which the first P type impurity region and the second P type
impurity region are layers disposed in different directions. (6)
The image sensing device according to any one of (1) to (5) above,
in which the first N type impurity region and the second N type
impurity region are layers disposed in different directions. (7)
The image sensing device according to any one of (1) to (6) above,
in which the first N type impurity region is configured of an N+
region having a high concentration and an N- region having a low
concentration. (8) The image sensing device according to any one of
(1) to (7) above, in which the first N type impurity region is the
N- region having a low concentration. (9) The image sensing device
according to (2) above, in which a potential gradient is provided
from the capacity expansion part to the readout electrode for
reading out the electric charge. (10) The image sensing device
according to any one of (1) to (9) above, in which the second N
type impurity region in the capacity expansion part is formed
square in a cross-section viewed from a predetermined direction.
(11) The image sensing device according to any one of (1) to (9)
above, in which the second P type impurity region in the capacity
expansion part is formed curve having a predetermined width in a
cross-section viewed from a predetermined direction. (12) The image
sensing device according to any one of (1) to (9) above, in which
the second P type impurity region in the capacity expansion part is
formed circle having a predetermined width in a cross-section
viewed from a predetermined direction. (13) The image sensing
device according to any one of (1) to (12) above, in which the
capacity expansion part includes second P type impurity regions and
second N type impurity regions, the second P type impurity regions
and the second N type impurity regions being disposed alternately,
the repeat distance of the second P type impurity region and the
second N type impurity region being 1 .mu.m or less. (14) The image
sensing device according to any one of (1) to (13) above, in which
a plurality of the image sensing devices share a floating
diffusion, and the readout electrode is disposed near the floating
diffusion. (15) An imaging device comprises a first pixel disposed
in a substrate. The first pixel may include a first material
disposed in the substrate, and a second material disposed in the
substrate. A first region of the first material, a second region of
the first material, and a third region of the second material form
at least one junction. A first lateral cross section of the
substrate intersects the at least one junction, and a second
lateral cross section of the substrate intersects at least one
fourth region of the first material. (16) The imaging device of
(15), wherein the at least one fourth region of the first material
occupies a greater amount of surface area in the second lateral
cross section than the first region of the first material and the
second region of the first material occupy in the first lateral
cross section. (17) The imaging device of (15), further comprising:
an electrode on the substrate to read out electric charge. (18) The
imaging device of (15), wherein the first material is an n-type
material, and the second material is a p-type material. (19) The
imaging device of (15), wherein the first material is an n-type
material and the second material is an insulating material. (20)
The imaging device of (15), wherein the first lateral cross section
is taken closer to a light incident side of the first pixel than
the second lateral cross section. (21) The imaging device of (15),
wherein the first material and the second material form a lattice
structure in the first lateral cross section. (22) The imaging
device of (21), wherein the first material and the second material
are in a checkered pattern. (23) The imaging device of (21),
wherein the first material forms a grid of n columns and m rows in
the second material. (24) The imaging device of (21), wherein the
second material forms a grid of n columns and m rows in the first
material. (25) The imaging device of (15), wherein the first
material and the second material have linear shapes in the first
lateral cross section. (26) The imaging device of (15), further
comprising: a charge accumulation region disposed in the substrate.
(27) The imaging device of (26), wherein the at least one fourth
region of the first material occupies a greater amount of surface
area in the second lateral cross section than the first region of
the first material and the second region of the first material
occupy in the first lateral cross section. (28) The imaging device
of (26), further comprising: a second pixel, wherein the first
pixel and the second pixel share the charge accumulation region.
(29) The imaging device of (28), further comprising: a first
electrode on the substrate of the first pixel; and a second
electrode on the substrate of the second pixel, wherein the first
electrode and the second electrode readout electric charge from the
charge accumulation region. (30) The imaging device of (29),
wherein the first pixel and the second pixel are adjacent to one
another and the charge accumulation region is between the first
electrode and the second electrode. (31) The imaging device of
(26), further comprising: a second pixel, a third pixel, and a
fourth pixel, wherein the first pixel, the second pixel, the third
pixel, and the fourth pixel share the charge accumulation region.
(32) The imaging device of (31), further comprising: a first
electrode on the substrate of the first pixel; a second electrode
on a substrate of the second pixel; a third electrode on a
substrate of the third pixel; and a fourth electrode on a substrate
of the fourth pixel, wherein the first electrode, the second
electrode, the third electrode, and the fourth electrode readout
electric charge from the charge accumulation region. (33) The
imaging device of (32), wherein the first pixel, the second pixel,
the third pixel and the fourth pixel are in a 2.times.2 matrix, and
the charge accumulation region is at a center portion of the
2.times.2 matrix. (34) The imaging device of (33), wherein the
charge accumulation region is surrounded by the first electrode,
the second electrode, the third electrode and the fourth
electrode.
REFERENCE SIGNS LIST
[0216] 10 Image sensing device [0217] 21 P+ region [0218] 22 N+
region [0219] 23 N- region [0220] 24 P+ region [0221] 25 P+ region,
substrate [0222] 300 image sensing device or imaging device [0223]
301 N- region [0224] 302 N+ region [0225] 303 P+ region [0226] 310
PN junction capacity expansion part [0227] 320, 420 N type impurity
region [0228] 330, 410 P type impurity region [0229] 500 image
sensing device or imaging device [0230] 501 N- region [0231] 600
image sensing device or imaging device [0232] 601 P+ equivalent
region [0233] 610 PN junction capacity expansion part [0234] 701
floating diffusion or charge accumulation region [0235] 1000 image
sensing apparatus or imaging apparatus [0236] 1001 lens group
[0237] 1002 image sensing device or imaging device [0238] 1003 DSP
[0239] 1004 frame memory [0240] 1005 display [0241] 1006 recording
unit [0242] 1007 operation unit [0243] 1008 power source [0244]
1009 bus line
* * * * *